Heart diseases including arrhythmias and heart failure are the No. 1 cause of death in the adult population in the United State and many other countries. In order to develop better and more effective therapies to treat heart diseases, it is critically important for scientists and physicians to obtain in-depth and accurate understanding of the heart disease mechanisms. In the recent several decades, researchers in the field have been accumulating more and more experimental data in studying the heart diseases mechanisms at multi-scale from molecular, to cellular, and to tissue and organ levels. However, important conceptual advances in the cardiac field require integration of the knowledge learned at all these levels. Now is the time to take the necessary step forward to integrate the experimental data into quantitative models which will enable researchers to use mathematical tools and computational power to unravel the dynamic interactions of the molecules and cells in the heart. The unique design of this conference series is to combine experimental study and mathematical modeling iteratively to achieve in-depth understanding of the dynamic systems that control cardiac E-C coupling and arrhythmias. The proposed interdisciplinary conference is the fourth in this series; the first three conferences have received overwhelmingly positive evaluations from the scientific community. This conference will combine the experimental and modeling studies in the field of K+ channels, with focused topics on K+ channel structure, function, regulation, their interaction with Ca2+ homeostasis and in connection to arrhythmias and HF. The emphasis are on summarizing current state of research in the focus area, identifying consensus and controversy (where more investigation is needed), giving experimentalists access to modeling tools and modelers a deeper understanding of the data that must drive their modeling efforts. Our conference will address how the ion channel properties (and changes thereof) have consequences at more integrative cellular and whole heart levels, so the participants will gain multi-scale comprehensive perspectives. This conference also facilitates exchange of the ideas, data, and information among the experimentalists and modelers in order to develop interdisciplinary collaborations. The conference results will be published in leading scientific journals in the form of comprehensive reviews which have broad impact on research community. Narrative: Cardiac arrhythmias and heart failure are the #1 cause of death in the United States and developed world. We propose to hold an interdisciplinary conference to bring together internationally renowned experimentalists and computational modelers in the cardiac research field. The goal is to achieve quantitative in-depth understanding of the molecular and cellular mechanisms that cause heart diseases. Understanding the disease mechanisms is critically important for developing new therapeutic strategies to effectively treat heart diseases.